Effects of isoflavone interventions on bone turnover markers and factors regulating bone metabolism in postmenopausal women: a systematic review and meta-analysis of randomized controlled trials

This study examined how isoflavone interventions impact bone health in postmenopausal women. Analyzing 73 trials found that isoflavones reduce bone resorption markers, enhance bone minerals, and increase hormones regulating bone metabolism. This suggests that isoflavones could help address bone health issues in postmenopausal women. Purpose This study aimed to assess the impact of isoflavone interventions on bone turnover markers and various biochemical markers of bone metabolism through systematic review and meta-analysis. Methods Four electronic databases, including PubMed, Embase, Scopus, and Cochrane Library, were searched in September 2023 for investigating the effects of isoflavones on bone turnover markers as well as signaling molecules regulating osteoclast differentiation, bone minerals, and hormones regulating bone metabolism in postmenopausal women. The main effect estimates, obtained using a random-effects model, were summarized using the mean difference (MD) or standardized mean difference (SMD), as appropriate. Results A total of 73 randomized controlled trials were included, comparing an isoflavone intervention to a placebo. Our findings demonstrated that isoflavone interventions significantly reduced bone resorption markers, that is, beta cross-linked C-telopeptide of type 1 collagen (beta-CrossLaps) (MD = - 0.0943 ng/mL; P = 0.0071) and pyridinoline (PYD) (SMD = - 0.9111; P = 0.0247). Moreover, isoflavone interventions positively affected bone mineral parameters by increasing serum calcium levels (MD = 0.3430 mg/dL; P = 0.0267) and decreasing serum phosphorus levels (MD = - 0.0648 mg/dL; P = 0.0435). Hormones involved in regulating bone metabolism, particularly insulin-like growth factor type 1 (IGF-1), exhibited significant increases following isoflavone interventions (MD = 9.8163 ng/mL; P < 0.0001). Subgroup analysis suggested that the effects of isoflavones on bone turnover markers are influenced by factors such as the duration since menopause and the intervention duration. Conclusion This systematic review and meta-analysis highlight the potential of isoflavone interventions to rectify imbalances in bone remodeling, enhance bone mineral homeostasis, and optimize hormones regulating bone metabolism in postmenopausal women.